I recall John posting something on his forum about taking a break from manufacturing the Tap-X autoformer units. However, he did offer to build a balanced one for me, so maybe he's back to doing them in small runs or one-offs.
To me one of the best passive preamps out there is the Lightspeed Attenuator. There is one here for sale that came up today.
I never heard the Music First units, but I had a passive preamp using S&B transformers that I liked. These are the transformers used in the Music First line. However, as mentioned the Music First units are over priced.